Various methods and devices have been described for determining the position of a probe or catheter tip inside the body using electromagnetic fields, such as in U.S. Pat. No. 5,042,486 and PCT patent publication No. WO 94/0938, whose disclosures are incorporated herein by reference. Other electromagnetic tracking systems, not necessarily for medical applications, are described in U.S. Pat. Nos. 3,644,825, 3,868,565, 4,017,858, 4,054,881 and 4,849,692, whose disclosures are likewise incorporated herein by reference.
U.S. Pat. No. 5,391,199, filed Jul. 20, 1993, which is assigned to the assignee of the present patent application and whose disclosure is incorporated herein by reference, describes a system that incorporates a catheter, which includes a position measuring device that can determine the position of the catheter in three dimensions, but not its orientation.
PCT patent application No. PCT/US95/01103, which is likewise assigned to the assignee of the present patent application and whose disclosure is incorporated herein by reference, describes a catheter system including means for determining the six-dimensions of position and orientation of the catheter's distal tip. This system uses a plurality of non-concentric coils adjacent to a locatable site in the catheter, for example near its distal tip. Preferably three orthogonal coils are used. These coils generate signals in response to externally applied magnetic fields, which allow for the computation of six position and orientation coordinates, so that the position and orientation of the catheter are known without the need for imaging the catheter.
U.S. Pat. No. 5,383,874 (Jackson et al.) describes a system for identifying and monitoring catheters, including identification means carried within the handle of the catheter body. In one embodiment of the invention of this patent, the handle includes a solid-state microchip pre-programmed with a digital value representing the catheter's identification code and other operational and functional characteristics of the catheter. The handle is connected by a cable to a control console, which reads data from the microchip. In one disclosed embodiment, the microchip may record the number of times the catheter has been used. Digital data storage in the catheter handle adds multiple digital signal wires to the catheter.